The present invention relates to a technology of personal authentication using biological information, and more particularly, to a technology of performing personal authentication based on a plurality of types of biological information in an integrated manner.
In recent years, with the development of electronic commerce on a network, increased importance of control of entrance/exit into/from a place requiring physical security, and the like, personal authentication technology has received attention. Among others in the personal authentication technology, particular attention has been focused on individual identification techniques using information on human biological features (biometrics). As usable biological features, a fingerprint, an iris, a blood-vessel arrangement in a retina, a face, a voiceprint and the like have been proposed.
However, when each type of biometric personal authentication is employed singly, the following problems arise:
(1) the authentication performance is limited, and
(2) a certain user may fail to join the authentication system due to injury of the biological spot used for authentication and the like.
As for the problem (1), some techniques have been proposed for improving the authentication performance by integrating a plurality of types of biological information (see Japanese Laid-Open Patent Publication Nos. 8-16788, 11-253426, 11-306351 and 2000-242786, for example).
In Japanese Laid-Open Patent Publication No. 8-16788, a plurality of types of biological information are acquired from a person to be authenticated. Feature parameters captured are divided into a plurality of categories. The categories are respectively weighted according to the degree of distinction of the features of the person from others and then integrated. The integrated result is compared with a threshold to thereby identify the person.
In Japanese Laid-Open Patent Publication No. 11-253426, a comparison score vector is generated using the number of comparison scores for each biological feature comparing section as the number of dimensions, and classified into either a “valid” or “invalid” category using linear discrimination, quadratic discrimination, a neural network or statistical probability in a vector space.
In Japanese Laid-Open Patent Publication No. 11-306351, a plurality of comparison scores for each biological feature comparing section are normalized with respective probabilities and integrated using the weighted sum or weighted product of the probabilities.
In Japanese Laid-Open Patent Publication No. 2000-242786, a plurality of authentication results for each biological feature comparing section, which correspond to “valid” or “invalid”, are integrated using logical OR or logical AND.
All of the above conventional techniques focus on how to integrate authentication results determined from a plurality of types of biological information. In other words, while these are techniques relating to “multimodal authentication” using a plurality of types of biological information in combination, the types of biological information used are predetermined and all the types of biological information must be acquired invariably during authentication as a premise. The technique described in Japanese Laid-Open Patent Publication No. 8-16788 adopts weighting for a category in which a feature of the person is less distinctive, so that such a category is not reflected in the authentication criteria. However, during authentication, all the types of biological information must be entered as a premise.
The problem (2) that a certain user may not use some biological information will then be discussed.
Suppose a user has a finger unsuitable for fingerprint authentication (for example, the fingerprint pattern is unclear due to a chemical or friction, or the user has a dry skin unfit for a semiconductor fingerprint sensor). In the conventional techniques, the user must enter a plurality of types of biological information including “fingerprint” predetermined for an authentication device during authentication without being notified of the fact that his or her fingerprint is unfit for the authentication. This impairs the convenience of the user.
In addition, the number of types of biological information entered may be reduced when part of the biological information of the user is unfit for authentication, or some type of biological information is temporarily unusable due to injury and the like. In such a case, attainment of the effect characterizing the “multimodal authentication”, that is, improving the authentication performance by use of a plurality of types of biological information in combination, may become difficult, and thus the authentication performance may be deteriorated.
The number of types of biological information entered may also be reduced when entry of some type of biological information is difficult under certain circumstances, such as that entry of “voiceprint” is difficult under noisy circumstances. In such a case, also, the problem described above may occur and the authentication performance may be deteriorated.